Method of impregnating a porous ferrous part with copper



United States Patent M METHOD OF IMPREGNATING A POROUS FERROUS PART WITHCOPPER Paul I. Shipe, Xenia, Ohio, assignor to General MotorsCorporation, Detroit, Mich., a corporation of Delaware No Drawing.Application May 25, 1953, Serial No. 357,338

6 Claims. (Cl. 117-37) This invention relates to impregnation processesand is particularly directed to the impregnation of porous ferrous partswith a cupreous material.

. It is one of the objects of the invention to provide a method forimpregnating porous ferrous parts with copper or other cupreous metalswherein the impregnated ferrous part is free from channels, pits orother surface imperfections due to the impregnation process.

In carrying out this object, it is a further object to supply suflicientferrous metal with the cupreous metal used as the impregnant to satisfythe dissolving action of copper for iron prior to the time that saidcupreous metal infiltrates the porous iron part and to also includesuflicient non-metals in the impregnant material to prevent adhesion ofexcess ferrous metal to the surface of the ferrous part.

This object is accomplished by utilizing iron in the form of cast ironpowder, which cast iron includes graphitic carbon that acts as thenon-metal and in mixed form with the cupreous metal acts as aretardenttoward flow of molten cupreous metal from the mixture untilsuch time that full distribution of ferrous metal in the impregnant hasoccurred. In this manner, when the cupreous metal actually infiltratesthe ferrous part, cupreous metal has had its dissolving action fullysatisfied whereby no further erosion occurs.

Numerous methods have been proposed for preventing erosion of porousferrous materials by copper and copper alloys when said ferrous metalsare infiltrated with copper. This infiltration process is one of highutility since a copper or copper alloy impregnated into a porous ferrouspart adds strength to the part, reduces its porosity and therebygenerally improves the physical characteristics of the part. metals areinfiltrated into porous ferrous parts, there is a tendency towarderosion at the surface due to the dissolving tendencies of copper oniron. Past processes for controlling this tendency are disclosed inBourne Patent No. 2,401,221, assigned to the assignee here, wherein ironpowder is added directly to the copper impregnant, which procedurereduces the erosion tendency considerably. However, when largequantities of copper or copper alloys are desired to be impregnated intoa selected area of a porous ferrous part, there is still some erosivetendency due to the concentration of copper at the point of entry.

The major portion of the erosive tendency can be controlled but inproduction processes, it is desirable to utilize a broad range ofimpregnation temperatures whereby the erosive tendencies are oftenaggravated. Another factor which causes difiiculty, is the tendency ofcopper to dissolve more iron at the impregnating temperature than willremain in combination therewith at the freezing point. In other words,as the temperature rises, the erosive tendency of copper on ironincreases. This condition obviously suggests that the most desirableinfiltrating conditions can be promoted by actually dissolving iron inthe cupreous metal at the impregnating tem- As previously explained,when cupreous 2,778,742 Patented Jan. 22, 1957 perature and prior to thetime that the cupreous metal is drawn into the porous ferrous part. Inorder to accomplish this end, Shigley applications, Serial Nos. 357,181and 357,182, filed concurrently herewith (MP-157 and MP-2l3) andassigned to the assignee of the present invention suggest the use ofcompacts of cupreous metal, ferrous metal and a non-metallic material,such as magnesium oxide, which mixture with an excess of ferrous metaltherein is briquetted into a compact of the shape and size desired andis placed on the porous ferrous part and heated therewith. When thetemperature exceeds the melting point of the cupreous metal, meltingoccurs and simultaneously the molten cupreous metal commences todissolve the associated ferrous material. This condition continues untilthe dissolving action of copper for iron'is fully satisfied. Themagnesium oxide acts in this instance as a sponge to maintain thismolten impregnant therein until such time that equilibrium temperatureconditions are obtained between the impregnant and the ferrous partbeing impregnated, whereupon the molten impregnating metal is drawn intothe porous fer rous part by capillarity.

This invention attacks the same problem in a slightly different manner.I have found that a similar result can be obtained by mixing thecupreous impregnant with cast iron powder. This cast iron powder notonly supplies the ferrous metal which is to be dissolved by the cupreousimpregnant prior to infiltration thereof into the porous ferrous part,but likewise, supplies the nonmetallics required to act as. a sponge forholding the molten impregnant until equilibrium temperature conditionsare obtained between the impregnant andthe part to be impregnated. Thesenon-metallic materials normally found in cast iron are mainly graphiticcarbon, silicon and its derivatives, etc.

Thus if cast iron turnings or powder for example, are properly graded,preferably to a -l00 mesh powder, this powder will contain sufficient ofthe so called nonmetallics to create the desired condition. This castiron powder is then thoroughly mixed with copper powder, or copper alloypowder in a desired quantity to provide suflicient cupreous metal toimpregnate the porous ferrous part as desired. Preferably, the mixtureof the cast iron powder and the cupreous metal powder is briquetted intoa self-sustaining mass.

I have found that the cast iron powder should be in quantities rangingfrom 1 to 5% by weight of the total impregnant used which may be copperor copper alloy or may be copper, for example, with some zinc, tin orother alloying ingredient. In any case, the cast iron powder supplies,sufiicient iron to satisfy the dissolving action of copper or iron andsimultaneously, due to the nonmetallics, acts as a retardent toward theimmediate flow of the molten constituent. After the porous ferrous parthas been impregnated, the residue of the impregnant material may bebrushed 01f the surface of the part due to the fact that the graphiticcarbon, silicon, etc., prevents any firm adhesion of the residue to thesurface of the porous ferrous part. In this manner,-an excess of castiron powder maybe utilized with no deleterious results such as stickingto the surface of said part and thereby marring said surface due to theremoval of the adhered parts.

In practice, it is desirable to briquet the impregnant material into ashape and size approximating the shape of the surface of the part to beimpregnated particularly where selective impregnation is required.Sufiicient metal is supplied to the compact to provide the adequate anddesired quantities of the cupreous metal in the porous part.

impregnation is carried out at temperatures above the melting point ofcopper and below the melting point of iron and preferably within therange of 2000 F. and 2150 'F. The -heating may be carried out byinduction if selective impregnation is comprehended, but preferably iscarried out by standard furnace heating. Usual non-oxidizing atmospheresshould be .used n all cases to facilitate the impregnation.

It is to be understood that cast iron powder as referred to herein maybe powder from white cast iron, gray cast iron or any of theconventional cast irons as known commercially.

While the embodiments of the present invention as herein disclosed,constitute preferred foims, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. In a method for impregnating a porous ferrous part with a cupreousmetal wherein the ferrous part, after impregnation, is substantiallyfree from pits, channels and .the like, the steps comprising; mixing adesired quan .tity of cupreous metal with from 1 to 5% by weight thereofof cast iron powder, placing said mixture upon said ferrous part to beimpregnated in a desired position relative thereto, heating the ferrouspart with the mixture .of cupreous metal and cast iron powder thereontoa temperature above the melting point of .the cupreous metal. andbelow the melting point of iron fora time sufficient to obtainequilibrium temperature conditions in said mixture and said partwhereupon sa-id cupreous metal dissolves a desired portion .of the ironin lthe cast ,iron and then infiltrates said ferrous part, and finallyremoving any .residueof said mixture from-said infiltrated part.

2. In .a method for impregnating a porous ferrous part with a cupreousmetal wherein the ferrous part, after impregnationjis substantially.free from pits, channels and the like, .the steps comprising; mixi gfidesired quantity of .cupreous metal with :from 1 to 5% by weight thereofof .castiron powder, briquetting said mixture intoaselfsustainingcompact of ,a .desired shape, placing said compact uponthe ferrous part .to .be impregnated and in a desired position relativethereto, .heatingdhe ferrous part and the compact 'to a temperatureabove the meltingpoint of the cupreous metal and below the meltingpointof iron .for a .time sufficient to obtain equilibrium temperature.conditions betweensaidco-mpactrand said part whereupon said.cupreousmetal dissolves .a portion of the iron in the cast iron andlthen'infiltrates said ferrous part, and finally removing anyresiduetofsaidcompactfromsaid infiltrated :part.

3. In a method for impregnating aporous ferrous part with acupreousmetalwherein the ferrous ,part,,after impregnation, is substantially freefrom pits, channels .and .the like, the st pscomprising; mixingacupreous metal .in a predetermined quantity with cast iron powder in-..cluding sufficient iron to.fully satisfy the dissolving action ofcopper or ironatthe impregnating temperature, placing said :mixtureupon,thesferrouspart .in proxirnityto the area thereof to be impregnated,dissolving at .least aportion .of ,the iron in :said cast, iron intosaid ,cupreous metal by heating the mixture and .the -partsimultaneously to a temperature above the .melting point of the cupreous.metal-and'below-t-he melting point of iron fora time suf- .ficient .toobtain equilibrium temperature conditions between the mixture and thepart, causing said 'cupreous metal to then infiltrate-said part onlyafter said equilibrium is obtained by drawing said molten impregnant bycapillarity into the pores of said part and finally removing any residueof said mixture from said part.

4. In a method for impregnating a porous ferrous part with a cupreousmetal wherein the ferrous part, after impregnation, is substantiallyfree from pits, channels and the like, the steps comprising; mixing apredetermined quant y o upr ous m ta Po de w th cas iron powder inamounts to provide suflieient iron to fully satisfy the dissolvingaction of copper for iron at the imp es s pera ur hr que t n sa d ix u einto a compact, placing said compact upon said part and in proximity tothe area thereof to be impregnated, dissolving at least a portion of theiron in said cast iron powder into said cupreous metal by heating themixture and the part simultaneously to a temperature above the meltingpoint of the cuprcous metal and below the melting point of iron for atime sulficient to obtain eguilibrium temperature conditions between thepart and the compact, then causing said cupreous metal to infiltrate theports of said porous ferrous part only after said equilibrium isobtained by drawing the molten impregnant by capillarity into the poresof the part and finally removing any residue of said compact from saidpart.

5. In a method for selectively impregnating predetermined portions of aporous ferrous part witha cuprctous metal while maintaining the ferrouspart substantially free from pits, channels and the like .at the surfacethereof, the steps comprising; providing a compact including apredetermined quantity of cupreous metal together with from 1 to 5% byweight thereof of cast iron powder having a particle size of at leastminus mesh said compact having a shape substantially similar to theshape of the area to be impregnated of said ferrous part, pla ng hecompa urea h e o pa ti the e r d Pos t n nd o tiguou o t a ea t b mp gnaselectively heating the ferrous part at that portion only .to beimpregnated to a temperature above the vmelting point f he unre u m taan be t m l n po n of iron While simu a e u y he tin d mpa t e ntinu ngsaid heat fo u a t me tha qui riumtemperature eonditions are obtainedbetween the part and the compact while progressively dissolvingsufiicient iron from said cast iron by said cupreous metal to fullysatisfy h dis o v n act o coppe on iron an the when equilibriumtemperature conditions have been obtained, causing said cupreous metalto infiltrate the selected heated portion of said porous ferrous partfor imp e at n e sa e and fin y m ng ny r sidue of said compact framsadpar The me hod as c ai e in .c aim 5, whe e the s l ct ve heating is acomp ishe y i du v y h ting a partion only of theferrous part.

References Cited in the file of thispatent UNI ED TATE E 1? 2,401,221{Bourne May '28, 19.46 2,422,439 Schwarzkopf June 117, :1947 2,481,962Whitfield Sept. :13, .1949 2,561,579 Lenel July '24, 1951 2715589 SmithAug. :16, 1:955

1. IN A METHOD FOR IMPREGNATING A POROUS FERROUS PART WITH A CUPREOUSMETAL WHEREIN THE FERROUS PART, AFTER IMPREGNATION, IS SUBSTANTIALLYFREE FROM PITS, CHANNELS AND THE LIKE, THE STEPS COMPRISNING; MIXING ADESIRED QUANTITY OF CUPREOUS METAL WITH FROM 1 TO 5% BY WEIGHT THEREOFOF CAST IRON POWDER, PLACING SAID MIXTURE UPON SAID FERROUS PART TO BEIMPREGNATED IN A DESIRED POSITION RELATIVE THERTO, HEATING THE FERROUSPART WITH THE MIXTURE OF CUPREOUS METAL AND CAST IRON POWDER THEREON TOA TEMPERATURE ABOVE THE MELTING POINT OF THE CUPREOUS METAL AND BELOWTHE MELTING POINT OF IRON FOR A TIME SUFFICIENT TO OBTAIN EQUILIBRIUMTEMPERATURE CONDITIONS IN SAID MIXTURE AND SAID PART WHEREUPON SAIDCUPREOUS METLA DISSOLVES A DESIRED PORTION OF THE IRON IN THE CAST IRONAND THEN INFILTRATES SAID FERROUS PART, AND FINALLY REMOVING ANY RESIDUEOF SAID MIXTURE FROM SAID INFILTRATED PART.